10. Cyclic AMP (cAMP) is important to cell function for all the following reasons EXCEPT: (A) it provides information about the extracellular environment. (B) it permits a large intracellular response to relatively weak extracellular signals. (C) it provides a site for integrating the metabolic requirements of cells. (D) it reversibly regulates enzymatic activity in cells. (E) it is a source of energy for cells.